Dynamic estimates of pressure and CO2-storage capacity in carbonate reservoirs in a depleted gas field, northeastern Thailand

Onshore geological storage of CO2 is focused in northeastern Thailand. This study presents a case study on numerical simulations of CO2 injection into Permian carbonate reservoir in the Sin Phu Horm gas field, which will become a depleted gas field in 2037. Schlumberger Petrel and ECLIPSE are used for reservoir modeling and simulation. One injection well located at the crest of the anticlinal structure is designed to perform injection of CO2 into the dolomite unit of the Pha Nok Khao Formation at approximately 2037 m from earth surface. This simulation of CO2 injection aims to verify cumulative amount of CO2 after injection and to predict reservoir pressure for 50 years. The results show that at the end of 50-year CO2 injection, reservoir pressure increases from 2478 to 2750 psi. The latest pressure remains below the initial pressure (3900 psi) at the beginning of production phase in 2007. With injection rate at 530 tCO2 per day or 0.19 MtCO2 per year up to 50 years, the total amount of injected CO2 in the reservoir is 9.5 Mt. This case study demonstrates that the dolomite reservoir of the Sin PHu Horm field can accommodate CO2 from constant injection rate at 530 tCO2 per day or up to 50 years. The findings can guide site selection decisions in Permian carbonate reservoirs for CO2 storage demonstrations.